W02008/089207A1 discloses a method for operating an access control system for controlling access to a secured area of a building such as a story or a section of a story. The access control system comprises a central computer unit and a door opener. The door opener grants access to the secured area. The central computer unit is communicatively connected to the door opener via network-supported access points. The door opener has a reader, which reads in an identification code from a mobile data carrier. The read-in identification code is checked either by the reader or by the central computer unit with an identification code in a list comprising valid identification codes for the secured area. Upon successful checking, the door opener grants access to the secured area.